Railway hopper cars have been used for many years to transport and sometimes store bulk materials. Hopper cars generally include one or more of hoppers which may be used to hold cargo or lading during shipment. Hopper cars are frequently used to transport coal, sand, metal ores, ballast, aggregates, grain and any other type of lading which may be satisfactorily discharged through respective openings formed in one or more hoppers. Discharge openings are typically provided at or near the bottom of each hopper to rapidly discharge cargo. A variety of door assemblies and gate assemblies along with various operating mechanisms have been used to open and close discharge openings associated with railway hopper cars.
Hopper cars may be classified as open or closed. Hopper cars may have relatively short sidewalls and end walls or relatively tall or high sidewalls and end walls. The sidewalls and end walls of many hopper cars are often formed from steel or aluminum sheets and reinforced with a plurality of vertical side stakes or support posts. Some hopper cars include interior frame structures or braces to provide additional support for the sidewalls.
Applicable standards of the Association of American Railroads (AAR) established maximum total weight on rail for any railcar including boxcars, freight cars, hopper cars, covered hopper cars, gondola cars, tank cars and temperature controlled railway cars within prescribed limits of length, width, height, etc. All railcars operating on commercial rail lines in the U.S. must have exterior dimensions which satisfy associated AAR clearance plates. Therefore, the maximum load which may be carried by any railcar is typically limited by AAR standards for total weight on rail, applicable AAR clearance plate and empty weight of the railcar. Reducing the empty weight of a railcar and/or increasing interior dimensions may increase both volumetric capacity and maximum load capacity of a railcar while still meeting applicable AAR standards for total weight on rail and AAR clearance plate.
Longitudinally oriented discharge openings and associated gates have several advantages over transversely oriented discharge openings and associated gates on railcars, highway trucks, or other equipment having hoppers due to generally lighter weights, increased load capacity, and quicker discharge rates. Transversely oriented discharge openings and gates may be coupled with a common linkage operated by an air cylinder. The air cylinder is typically mounted in the same orientation as the operating gate linkage which is often a longitudinal direction relative to the associated hopper. Transverse gates may also open and close by separate operating assemblies that cause synchronization problems and require adjustments. Longitudinally oriented discharge openings and gates for prior hopper cars have often been used in pairs that may be rotated or pivoted relative to the center sill or side sills of a hopper car.